Bluetooth: User Pairing Response restructuring

There are 4 possible User Responses to pairing requests,
and they all share the same checks and handling. This
restructures the handling of the two Confirm responses
in preperation for the second two.

Signed-off-by: Brian Gix <bgix@codeaurora.org>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>